I use the sonication method to lyse S. cerevisiae and quantify total protein extraction as a function of sonication time. Sometimes foam was formed, as the foam could mean protein denaturalization. Does this could affect the cuantification via Biuret?
Let the foam settles down. Extend or efficiency of sonication may affect the protein yield in supernatant but shall not affect protein quantification by Biuret method. Instead, use Bradford reagent for protein assay. It's more sensitive method than Biuret.
Hi Carlos Pacheco Pérez I think it is more likely that lipids are contributing to the foam you are seeing. Proteins usually don't foam in NaOH solutions. They precipitate.
Denaturation (like SDS may do) means an increase of peptide links reactive with Biuret, so you will overestimate your protein quantity as compared to undenatured one. This could be a mean to study the secondary structure of a protein since for example linear proteins are less affected by denaturation (less increase of Biuret coloration after denaturation) than globular proteins (important increase of Biuret coloration after denaturation).
Hi. I found this:
https://www.jstage.jst.go.jp/article/biochemistry1922/38/1/38_1_7/_pdf
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